blit

Agent-friendly terminal streaming — as fast as the network and browser allow. The server parses PTY output, diffs it, and sends only what changed — LZ4-compressed, per-client paced, WebGL-rendered. Adapts to any transport (WebSocket, WebTransport, WebRTC, Unix socket, SSH) and security model. AI agents get a full set of non-interactive CLI subcommands to create, control, and read terminal sessions programmatically. Embed the React component in any web app with blit-react.

blit-server &
blit                # opens browser

Or over SSH:

blit --ssh myhost

Install

macOS (Homebrew)

brew install indent-com/tap/blit indent-com/tap/blit-gateway indent-com/tap/blit-server

Debian / Ubuntu (APT)

curl -fsSL https://repo.blit.sh/blit.gpg | sudo gpg --dearmor -o /usr/share/keyrings/blit.gpg
echo "deb [signed-by=/usr/share/keyrings/blit.gpg arch=$(dpkg --print-architecture)] https://repo.blit.sh/ stable main" \
  | sudo tee /etc/apt/sources.list.d/blit.list
sudo apt update
sudo apt install blit blit-server blit-gateway

Nix

nix build .#blit-server      # or blit-cli, blit-gateway

Or jump to nix-darwin / NixOS for service configuration.

From source

nix develop        # or use direnv — .envrc is included
cargo build --release -p blit-cli -p blit-server -p blit-gateway

How it works

blit-server hosts PTYs and tracks full parsed terminal state. For each connected client it computes a binary diff against what that client last saw and sends only the delta — LZ4-compressed, with scrolling encoded as copy-rect operations.

blit-gateway is a stateless WebSocket/WebTransport proxy that authenticates browser clients and forwards traffic to the server over a Unix socket. PTYs survive gateway restarts.

blit (CLI) connects to a local or remote server (over SSH if needed), embeds a temporary gateway, and opens the browser. No separate deployment required.

blit-react is the React embedding library — the primary integration point for applications. See EMBEDDING.md.

The server paces each client independently based on render metrics the client reports back: display rate, frame apply time, backlog depth. A phone on 3G doesn't stall a workstation on localhost. The focused session gets full frame rate; background sessions throttle down. Keystrokes go straight to the PTY — latency is bounded by link RTT and nothing else.

For wire protocol details, frame encoding, and transport internals, see ARCHITECTURE.md.

Browser access

Pick one, not both:

• blit-gateway: standalone proxy for persistent browser access. Handles passphrase auth, serves the web app, optionally enables QUIC.
• blit (CLI): connects to the server, embeds a temporary gateway, opens the browser.

With the gateway:

BLIT_PASS=secret blit-gateway &
blit-server
# open http://localhost:3264

If building from source, substitute cargo run -p blit-server, cargo run -p blit-cli, etc. For the dev environment with hot-reloading, see CONTRIBUTING.md.

Running services

macOS (Homebrew)

brew services start blit-server
brew services start blit-gateway

Configuration lives in env files under $(brew --prefix)/etc/blit/:

echo 'export BLIT_PASS="secret"' >> $(brew --prefix)/etc/blit/blit-gateway.env
echo 'export BLIT_SCROLLBACK="50000"' >> $(brew --prefix)/etc/blit/blit-server.env
brew services restart blit-gateway blit-server

Debian / Ubuntu (systemd)

sudo systemctl enable --now blit@alice.socket

Manual (systemd)

sudo cp systemd/blit@.socket systemd/blit@.service /etc/systemd/system/
sudo systemctl daemon-reload
sudo systemctl enable --now blit@alice.socket

Configuration

blit-server

Variable	Default	Purpose
SHELL	/bin/sh	Shell to spawn for new PTYs
BLIT_SOCK	$TMPDIR/blit.sock, $XDG_RUNTIME_DIR/blit.sock, or /tmp/blit-$USER.sock	Unix socket path
BLIT_SCROLLBACK	10000	Scrollback rows per PTY

blit-gateway

Variable	Default	Purpose
BLIT_PASS	required	Browser passphrase
BLIT_ADDR	0.0.0.0:3264	HTTP/WebSocket listen address
BLIT_SOCK	$TMPDIR/blit.sock, $XDG_RUNTIME_DIR/blit.sock, or /tmp/blit-$USER.sock	Upstream server socket
BLIT_CORS	unset	CORS origin for font routes
BLIT_QUIC	unset	Set to 1 to enable WebTransport
BLIT_TLS_CERT	auto-generated	TLS cert for WebTransport
BLIT_TLS_KEY	auto-generated	TLS key for WebTransport

blit (CLI)

Variable	Default	Purpose
BLIT_SOCK	$TMPDIR/blit.sock, /tmp/blit-$USER.sock, /run/blit/$USER.sock, $XDG_RUNTIME_DIR/blit.sock, or /tmp/blit.sock	Unix socket path

For SSH targets, blit --ssh HOST forwards the remote Unix socket over SSH and opens the browser with an embedded local gateway.

Agent subcommands

The CLI includes non-interactive subcommands designed for programmatic / LLM agent use. All subcommands accept --socket PATH, --tcp HOST:PORT, or --ssh HOST to select the transport.

blit list                                      # List all PTYs (TSV: ID, TAG, TITLE, STATUS)
blit start htop                                # Start a PTY running htop, print its ID
blit start -t build make -j8                   # Start with a tag
blit start --rows 40 --cols 120 bash           # Start with a custom size
blit start --wait --timeout 60 make -j8        # Start and block until exit
blit show 3                                    # Dump current visible terminal text
blit show 3 --ansi                             # Include ANSI color/style codes
blit history 3                                 # Dump all scrollback + viewport
blit history 3 --from-start 0 --limit 50       # First 50 lines
blit history 3 --from-end 0 --limit 50         # Last 50 lines
blit history 3 --from-end 0 --limit 50 --ansi  # Last 50 with ANSI styling
blit send 3 "q"                                # Send keystrokes (supports \n, \t, \x1b escapes)
blit show 3 --rows 40 --cols 120               # Resize before capturing viewport
blit history 3 --cols 200                      # Resize before reading scrollback
blit wait 3 --timeout 30                       # Block until session exits
blit wait 3 --timeout 60 --pattern 'DONE'      # Block until output matches regex
blit restart 3                                 # Restart an exited session
blit close 3                                   # Close and remove a PTY

# Against a remote host
blit --ssh myhost list
blit --ssh myhost start htop
blit --ssh myhost show 1

Output is plain text with no decoration — designed to be easy for scripts and LLMs to parse. Errors go to stderr; non-zero exit on failure.

If you're building an AI agent that drives terminals, SKILLS.md is a ready-made skill definition — drop it into your agent's tool list and it can create, control, and read blit sessions out of the box.

What lives in this repo

Directory	Package	Role
crates/server/	blit-server	PTY host and frame scheduler
crates/remote/	blit-remote	Wire protocol and frame/state primitives
crates/browser/	blit-browser	WASM terminal runtime
crates/alacritty-driver/	blit-alacritty	Terminal parsing backed by alacritty_terminal
crates/gateway/	blit-gateway	WebSocket/WebTransport proxy
crates/cli/	blit	Browser client, agent subcommands, SSH tunnels
crates/fonts/	blit-fonts	Font discovery and metadata
crates/webserver/	blit-webserver	Shared HTTP helpers for serving assets and fonts
crates/demo/	blit-demo	Sample programs and test content
js/react/	blit-react	Workspace-based React client library
js/web-app/		Browser UI

How it compares

	blit	ttyd	gotty	Eternal Terminal	Mosh	xterm.js + node-pty
Architecture	PTY host + gateway	Single binary	Single binary	Client + daemon	Client + server	Library (BYO server)
Multiple PTYs	✅ First-class	❌ One per instance	❌ One per instance	❌ One per connection	❌ One per connection	⚠️ Manual
Browser access	✅	✅	✅	❌	❌	✅
Protocol	Binary frame diffs	Raw byte stream	Raw byte stream	SSH + prediction	UDP + SSP	Raw byte stream
Delta updates	✅ Only changed cells sent	❌	❌	❌	✅ State diffs	❌
LZ4 compression	✅	❌	❌	❌	❌	❌
Copy-rect scrolling	✅	❌	❌	❌	❌	❌
Per-client backpressure	✅ Render-metric pacing	❌	❌	⚠️ SSH flow control	❌	❌
Background session throttling	✅	❌	❌	❌	❌	❌
Server-side search	✅ Titles + visible + scrollback	❌	❌	❌	❌	❌
WebGL rendering	✅	❌	❌	❌	❌	⚠️ Addon
Transport	WS, WebTransport, Unix	WebSocket	WebSocket	TCP	UDP	WebSocket
WebTransport / QUIC	✅	❌	❌	❌	❌	❌
Embeddable (React)	✅	❌	❌	❌	❌	✅
Agent / CLI subcommands	✅	❌	❌	❌	❌	❌
Reconnect on disconnect	✅	✅	❌	✅	✅	❌
SSH tunneling built-in	✅	❌	❌	✅	✅	❌

Adjacent tools

tmux is the classic terminal multiplexer — windows, panes, session detach/reattach, all over a Unix socket. It's purely terminal-native: no browser access, no wire protocol beyond its own client-server IPC. blit handles the browser streaming side, so the two are complementary — you can run tmux inside a blit PTY.

Zellij is a terminal multiplexer (like tmux) — it manages panes, tabs, and layouts inside your existing terminal. It has a WASM plugin system, built-in search, multiplayer session sharing, and a beta web client. Where blit is a streaming stack that sends rendered frames to a browser, Zellij is a local-first workspace that happens to have a web escape hatch.

sshx is a collaborative terminal sharing tool. You run a single command and get a shareable URL with an infinite canvas of terminals, live cursors, and end-to-end encryption (Argon2 + AES). It uses a managed cloud mesh for routing, so there's no self-hosting. The focus is real-time pair programming, not persistent server access.

tmate is a tmux fork that gives you instant terminal sharing via a hosted relay. You get an SSH URL and a read-only web URL out of the box. It's the fastest path to "let someone else see my terminal" but doesn't do browser-native rendering, backpressure, or multi-session management.

Contributing

Building from source, running tests, dev environment setup, code conventions, and release process are all covered in CONTRIBUTING.md.

nix-darwin

{ inputs, ... }: {
  imports = [ inputs.blit.darwinModules.blit ];

  services.blit = {
    enable = true;
    gateways.default = {
      port = 3264;
      passFile = "/path/to/blit-pass-env";
    };
  };
}

NixOS

{ inputs, ... }: {
  imports = [ inputs.blit.nixosModules.blit ];

  services.blit = {
    enable = true;
    users = [ "alice" "bob" ];
    gateways.alice = {
      user = "alice";
      port = 3264;
      passFile = "/run/secrets/blit-alice-pass";
    };
  };
}